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TLK1221: EMI issue / other recommended device

Yusuke Mukuno
Expert 7395 points
Part Number: TLK1221

Hi Expert, 

My customer have an issue about EMI with TLK1221.

EMI noise frequency: 50MHz, 150MHz, 250MHz, ... 850MHz (100MHz step)

Could you please advice for reducing EMI noise method?

And, Could you please let me know your recommended devices for reducing EMI?

Data trans clock : 50MHz~100MHz
Parallel side data : 9 bits
Serial side data : one pair of differential
If possible, a transceiver (trans/recieve)
If possible, support SSCG function
Differential output voltage can be selected
Package is 7 mm square or less if possible

Thanks

Muk

  • 0
    TI__Mastermind 22272 points

    Hi Muk,

    I apologize for the delay in response.  It seems like you have a 50 MHz signal that is causing EMI (and odd harmonics of 50 MHz).  Can you help us better understand the source of the 50 MHz EMI?  If you disable the TLK1221, does the 50 MHz EMI remain present?  Also, do you happen to know the frequency of your recovered clock.  This should be measurable on RBC0.

    Thanks,

    Drew Miller

    HSSC Applications Engineer

  • 0 in reply to Drew Miller1
    Prodigy 20 points

    Hi Drew Miller,

     

    Thank you for your reply.

    No 50MHz EMI is observed when TLK1221 is disabled.

    The frequency of RBC0 is 100MHz.

    A one meter STP cable is used for communication.

    Spectrum analysis of the serial output TX by the TLK1221 matches the frequency of EMI.

    We believe that the TX is too strong.

    We think that EMI can be reduced by adjusting the amplitude of the differential voltage.

    If you have any idea about additional circuits for that purpose, it would be helpful.

     

    Thanks,

     

    Muk's customer

  • 0 in reply to user1947111
    TI__Mastermind 22272 points

    Hi Muk's Customer,

    I am not aware of any device settings that will reduce the amplitude of the TX differential voltage.

    It sounds like you may be running into a system level issue.  It may be necessary to investigate improving shielding of the circuit.  An additional thought is to remove the STP cable, terminate the connection, and see how this impacts the EMI.

    Thanks,

    Drew Miller

    HSSC Applications Engineer

  • 0 in reply to Drew Miller1
    Prodigy 20 points

    Hi Drew Miller,

    When we checked the transmition data, we found that the code was biased.

    By scrambling the data, we were able to confirm that there were less peaks in the spectrum analysis results.

    In addition, the amplitude of the differential signal could be adjusted by adding series resistors to the TX signals.

    We would like to take measures with this once.

    Thank you for your advice.

    Muk's Customer

  • 0 in reply to user1947111
    TI__Mastermind 22272 points

    Hi Muk's Customer,

    I'm glad you were able to make progress on the issue by changing the data pattern and inserting TX series resistors.

    Thanks,

    Drew Miller

    HSSC Applications Engineer